Propeller assemblies typically include multiple blades mounted to a hub, which is rotated by the engine. The hub typically defines a housing for a blade root of a propeller blade along with any retention mechanisms and pitch change mechanisms.
The blades can be line-removable and retained to the hub so as to supporting operating loads, including a centrifugal force component that acts in a direction parallel to the longitudinal axis of the propeller blade. Modern retention systems use an assembly of bearings to retain the propeller blade to the hub. Each blade root is retained within its own socket for rotation therein about a pitch change axis through use of the assembly of bearings. It is known to preload the bearings in order to maintain their stability under high centrifugal and thrust forces experienced during operation.